A measurement system with smooth draw-off disks is currently known. The disks have the task, on the one hand, of conveying the fiber sliver and, on the other hand, of measuring the thickness of the sliver. One of the disks is movably mounted. The movable draw-off disk is pressed to the rigidly mounted disk with a defined high pressure. The deflection of the movable mounted disk is evaluated as a measurement signal. A prerequisite for a usable measurement signal is the defined high force that must act on the fiber sliver and a very high rotational accuracy of the measuring rollers. After the measuring rollers, the sliver is conveyed into a tube. For this purpose, the sliver must run into the center of the tube, since otherwise no draw-off would be possible.
A roller drafting device for a spinning machine is known from DE 10 2011 051 552 A1. Therein, a roller drafting device for drafting at least one running strand-like stacked fiber composite a work station of a spinning machine, in particular at a spinning machine or a flyer, is proposed. In doing so, a drafting field is provided for each work station, which drafting field is formed between a pair of rollers on the inlet side and a pair of rollers on the outlet side, whereas a fiber guide device for guiding the stacked fiber composite is allocated to the drafting field. In this case, the fiber guide device features a fiber guide surface, which in turn features a three-dimensional structure, in particular an orange peel structure or a honeycomb structure. Such a three-dimensional structure prevents the sticking of the stacked fiber composite at the fiber guide surface through adhesion phenomena. However, the disadvantage In this case is that the orange peel structure or the honeycomb structure is difficult to manufacture.
A device for measuring the thickness of a textile fiber composite in a drafting system is known from EP 0 478 723 B1. The device features a pair of sensing rollers, one sensing roller of which, in the axis-center distance to the other sensing roller, can be changed according to the thickness of the fiber composite. In this case, the entire fiber composite can be guided between the pair of sensing rollers, and the sensing roller that is able to be changed in the axis-center distance can be pressed against the other sensing roller. The disadvantage in doing so is that, with such sensing rollers, this may lead to adhesion phenomena between the fiber composite and the sensing rollers, which prevents a straight exit of the fiber composite from the sensing rollers. Thereby, a depositing of the fiber composite that thereafter occurs in a container provided for this purpose is difficult to control. In order to reduce the adhesion phenomena, for example, the pressure with which a sensing roller is pressed on the other sensing roller can be reduced. However, the measurement of the thickness of the fiber composite is thereby distorted. Thus, a reduction of the contact pressure of one sensing roller on the other sensing roller is rendered inapplicable.
In particular, when fine slivers are processed, the described adhesion phenomena arise. The fine sliver is entrained and deflected by the smooth roller, and thereby can no longer be conveyed into the tube. Processing is no longer possible. Previously, this effect could only be counteracted by reducing the pressing force at the movably mounted roller to the extent that a reasonably straight run was achieved. However, the reduction of the pressing force also brings about a weakening or the complete failure of the measurement signal. The monitoring of the quality parameters, including the off-limit disable function, of the exiting sliver is no longer possible.